Commit 53b1a742 authored Jun 29, 2017 by Dave Martin Committed by Will Deacon Jun 29, 2017

arm64: ptrace: Avoid setting compat FP[SC]R to garbage if get_user fails



If get_user() fails when reading the new FPSCR value from userspace
in compat_vfp_get(), then garbage* will be written to the task's
FPSR and FPCR registers.

This patch prevents this by checking the return from get_user()
first.

[*] Actually, zero, due to the behaviour of get_user() on error, but
that's still not what userspace expects.

Fixes: 478fcb2c ("arm64: Debugging support")
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 15ad6ace

arch/arm64/kernel/ptrace.c

+4 −2

Original line number	Original line	Diff line number	Diff line
	@@ -947,9 +947,11 @@ static int compat_vfp_set(struct task_struct *target,

	if (count && !ret) {		if (count && !ret) {
	ret = get_user(fpscr, (compat_ulong_t *)ubuf);		ret = get_user(fpscr, (compat_ulong_t *)ubuf);
			if (!ret) {
	uregs->fpsr = fpscr & VFP_FPSCR_STAT_MASK;		uregs->fpsr = fpscr & VFP_FPSCR_STAT_MASK;
	uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK;		uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK;
	}		}
			}

	fpsimd_flush_task_state(target);		fpsimd_flush_task_state(target);
	return ret;		return ret;